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Chapter 2 Introduction to RAID
7
ADAC Ultra2 S466 – Host-Based RAID Solution
RAID products are either:
• host-based or
• SCSI-to-SCSI.
The ADAC Ultra2 S466 controller is a host-based RAID
solution. ADAC Ultra2 S466 is a PCI adapter card that is
installed in any available PCI expansion slot in a host
system.
Host-Based A host-based RAID product puts all of the RAID
intelligence on an adapter card that is installed in a network
server. A host-based RAID product provides the best
performance. ADAC Ultra2 S466 is part of the file server,
so it can transmit data directly across the computer’s buses
at data transfer speeds up to 132 MB/s.
The available sequential data transfer rate is determined by
the following factors:
•
the sustained data transfer rate on the motherboard
PCI bus,
•
the sustained data transfer rate on the i960RP PCI to
PCI bridge,
•
the sustained data transfer rate of the SCSI controller,
•
the sustained data transfer rate of the SCSI devices,
•
the number of SCSI channels, and
•
the number of SCSI disk drives.
Host-based solutions must provide operating system-
specific drivers.
SCSI-to-SCSI A SCSI-to-SCSI RAID product puts the RAID intelligence
inside the RAID chassis and uses a plain SCSI Host
Adapter installed in the network server. The data transfer
rate is limited to the bandwidth of the SCSI channel. A
SCSI-to-SCSI RAID product that has two wide SCSI
channels that operate at speeds up to 80 MB/s must
squeeze the data into a single wide SCSI (40 MB/s)
channel back to the host computer.
In SCSI-to-SCSI RAID products, the hard drive subsystem
uses only a single SCSI ID, which allows you to connect
multiple drive subsystems to a single SCSI controller.